Mounting of surface mounted components involves a number of problems compared to the old technique of mounting components, the leads of which are mounted in holes. These problems are as follows:
(1) The components are placed on a surface. The mounting error will therefore be continuously variable which leads to boundary problems between acceptable and unacceptable mounting. The old art components have a binary mounting error which means that either all leads are in their holes or they are not.
(2) There are different reasons for an increased interest to glue the components before soldering. This puts increased demands on the mounting position. Up till now the components have mostly been mounted on soldering paste. During the soldering operation surface tension phenomena will cause an automatic centering of the component. However, if the component is glued this centering effect will be eliminated.
(3) The components are small. The distance between the leads on a component old in the art is almost always 2.54 mm or more. For surface mounted components it is 1.27 or 0.80 mm and will decrease in the future.
(4) Machines for mounting of components old in the art utilize guiding holes which are drilled in the same operation as those in which the components should be mounted. The errors between the guide holes and the component holes will therefore be relatively insignificant.
(5) The components are so small that they mostly cannot be provided with identifying text. This increases the demand to measure the component electrically before mounting to ensure that the correct component will be mounted.
Items 1-4 above will together present great difficulties when mounting components with a lead distance of 1.27 mm and less by gluing. The enterprise Elektronikcentralen i Denmark which is well known in the Nordic countries has issued a study No. ECR-143 with the title "Leadless components" and in the fifth chapter, page 15, they have reached the conclusion that "from the present prerequisits the only solution now is to utilize manual mounting only and thereby introduce an optical correction of certain tolerances".
The actual Swedish production of surface mounted components with the lead distances 1.27 and 0,80 mm is often handmade even in the simpler case when the components are not glued.
Existing machines for surface mounting reflect the statements made above. These machines can be divided into different types, namely:
specialized machines which can only mount components having a size within very narrow limits, e.g. from 2.times.0.8 mm up til 3.2.times.2.0 mm. These machines often have high capacity and a high price.
Module machines are built up by a number of mounting stations each of which is specialized for a certain group of components of the same of almost the same size and design. Thus, a customer who uses many different component types must have a number of modules and will therefore have to pay a high price.
Machines without a centering operation fetch the components and move them. Thus, all errors in the fetch point component position will remain after the mounting operation.
The apparatus according to the invention makes it possible to arrange both effective centering and possibilities for connecting the component to an electronic measuring equipment with a minimum of mechanical components.